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Laser Technique Measures 'Real-Time' Auto Emissions

Photonics.comMar 2004
LIVERMORE, Calif., March 23 -- Using a unique laser-based, soot-heating technique, a team led by researchers at Sandia National Laboratories' Combustion Research Facility (CRF) has demonstrated the ability to measure "real world" particulate emissions from a vehicle under actual driving conditions.
Although on-board measurements of gaseous emissions are routine, real-time particulate measurements have been elusive -- but they are essential for validating federal emissions guidelines for vehicle compliance, Sandia said.

Pete Witze, an engineer in Sandia's CRF engine combustion department, recently collaborated with Artium Technologies, Chevron Oronite and the National Research Council (NRC) Canada to demonstrate the feasibility of obtaining on-board measurements of vehicle particulate emissions using laser-induced incandescence (LII) technology. LII is a non-intrusive diagnostic technology that can perform "real-time" measurements of particulate emissions produced by internal combustion engines. Artium, based in Sunnyvale, makes LII and phase doppler interferometry instruments.

Sandia, Artium and the NRC have worked together to develop the portable version of LII instrumentation that was used for the recent trial. Sandia said the new method may alter the way the automotive industry gauges particulate emissions.

During the past decade, CRF and NRC researchers honed the LII technique, discovered in the 1970s, and the NRC secured a temperature-measurement patent that is key to the current measurement capability.

In conducting the tests, Artium's LII instrument and ancillary equipment were placed in the trunk and on one side of the rear seat of a 2002 Volkswagen Jetta with automatic transmission and a turbocharged direct-injection diesel engine. An on-board diagnostics scan tool interface was used to access the vehicle and engine speeds for recording while the vehicle was driven on a test route in the Bay Area's Livermore Valley in northern California.

The most notable result during the recent tests, said Witze, was obtained during the coasting descent. "Although the vehicle speed and engine rpm were reasonably steady for the period from 470 to 600 seconds, the particulate emissions suggest that fuel injection cycled on and off intermittently."

Witze said the LII measurement technique, unlike other systems, does not require an operator in order to conduct the tests, and that engine manufacturers are "extremely interested" in LII. He will speak about on-board particulate emissions at the Coordinating Research Council's 14th On-Road Vehicle Emissions Workshop, to be held March 29 in San Diego.